In the prior art, the friction overrunning clutches are mainly in two types, one is roller/ball type based on wedging action of wedging mechanism, and the other is diagonal bracing type based only on friction self-locking. Both of the overrunning clutches are plane movement mechanisms having inner and outer rings with overly large hollowness. The structure characteristic of such clutches inherently determines that, for coping with the inner radial movement or planar rotation, it surely has structure defect and movement defect induced by roller, diagonal bracing, and spring, which can be only discretely arranged/exist, and it surely has the physical defect that the linear contacting friction pair and the idle resistance are in direct proportion with the rotating rate. Therefore, it is naturally determined that, in the clutch, the wedging angle/contacting angle is too small, the radial force is too large, and the radial rigidity is deficient. The circumferential discretely distributing of the radial force not only induces the severe stress condition of the intermediate member, such as the roller or diagonal bracing, but also maximizes the defect of deficient radial rigidity, such that the radial elastic deformation and resilience are both excessively large, and thus the actual wedging angle/contacting angle is not secured and the wedging/engaging process is not stable, the slippage angle is too large, wedging/engaging and dewedging/disengaging becomes difficult. As a result, the actual wedging angle/contacting angle is extremely sensitive to and in direct proportion to the geometric dimension variation of the inner and outer rings, the rollers, or the diagonal bracing due to wearing out and tearing apart, as well as elastic deformation at the radial stress point of the inner and outer rings. Movement between the individual members, such as the rollers or the diagonal bracing as well as movement between the different axial portions of any of individual members, are hard to be synchronized. The individual members are often clamped too tight or crushed, and the spring/retaining mount is more often deformed or broken consequentially. As for the diagonal bracing type clutches, it may become out of order due to overturning of the diagonal bracing.
The aforesaid defects lead directly to the shortcoming of low bearing capacity, low reliability, low transmission efficiency, difficulty in manufacture and assembly, high cost, tendency of being easily worn-out and torn-apart, limited applications of such clutches in the prior art (see “Current development and tendency of overrunning clutch”, Zhang Jizheng et al, the Third China-Japan International Conference on History of Mechanical Technology, Kunming, 2002, pp. 398-403). Because of lacking any better alternative technique, the overrunning clutches in the prior art are still the primary technique and products in the three application field of indexing, overrunning and backstop.
For more than 100 years, an overrunning clutch with ideal features has been searched. However, because of affection and preoccupation of the prior art, the working theory and physical essence of the planar wedging mechanism of the friction overrunning clutches are not thoroughly apprehended by the academic community and industrial community. In almost all the relevant documents, it is mistakenly believed that, the basic physical theory of torque transferring of the overrunning clutches depends on the frictionally self-locking (also known as self-locking conditions), particularly the frictionally self-locking of the two friction pairs of the wedging mechanism, and that slippage of the clutch on non-structural deformation/damage is due to the failure/destruction of the frictionally self-locking. Therefore, the people followed the suit unconsciously, i.e., seeking the resolutions and improvements only in the planar mechanism based on the conventional understanding. After exhausting almost all of the potentials of the planar friction mechanism, such as, the capability, structure, reliability, cost and work lifespan and so on, there was still no substantial improvement, and the search finally went to a dead end. Therefore, acquiring an ideal overrunning clutch became the technical difficulty desired to be resolved for a long time.
Although the patent reference CN2175321Y discloses a non-planar friction one-way overrunning clutch based on a one-way thread pair and a conical revolving friction pair, there isn't any useful information or indication therein ensuring that the clutch would have stable engagement to transfer the torque without slippage. It states only generally that there would be no slippage situation. Accordingly, this utility model patent would not actually achieve its stated purpose.
Additionally, the patent reference CN2479288Y also discloses a similar friction one-way overrunning clutch. And the patent references CN1292464A and CN2728825Y disclose two kinds of slider for motor vehicles with generally similar structure. Similarly, these three documents do not provide any useful information, indication or suggestion ensuring that the clutches would have stable engagement to assure transferring torque without slippage.